Inverse time-limit relay.



L. T. ROBINSON & c. v. HARDY.

INVERSE TIME LIMIT RELAY. APPLICATION FILED SEPT. 15, 1914.

Patented Feb. 11, 1919.

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LEWIS l7. EOBINSOl 'l AND CLYDE V. HARDY, Q SCHEN ECTADY, NEW YORK, ASBSIGNOM 136* GENERAL ELECTRIC COMPANY, A CORPGRATION NEW YORK.

:NvnasE TIME-LIMIT :annav.

i sensors.

Patented Feb. i1, leie.

Application filed September '15, 191.4. Serial No. 861,904.

- States, bot-h residing at Schenectady, in the county of Schenectady, State of New York, have invented OEIiJiLlIX new and useful 1m- 'p1.-ovements in Inverse Time-Limit Relays,

of which the following is a specification.

Our invention relates'to Inverse time limit relays and oarticularly to inverse time limit overload relays having two movable contact members adapted to control the circuit of the tripping coil of a circuit breaking device.

The object of our invention is broadly to. improve the construction of inverse time limit relays, thereby providing a relay of novel and improved construction. A more particular object of our invention'is to protwomovable contact members an arrangement whereby the minimum time of engagement of the contact membcrscan be simply, conveniently, and I accurately adjusted. A further object of our invention is to provide in a relay oltheabove mentioned type a novel and improved mechanism for actuating one of the movable contact members at a predetermineddefinite speed. A still further object of our invention is to provide an inverse time limit 'relay in which thecharacteristic relation between time and an electrical characteristic, such as current, may be suitably adjusted by convenient and simple means, and further to provide a relay inwhich accurate selective action for dillerent overloads and certainty of the cor-- rect order of "operation of circuit breaking switches under all conditions may .be satis factorily obtained. Other objects of our in-' vention Will be evident from the subsequent description of an inverse time limit overload relay embodying the invention.

The features of our invention which We consider pa-tentably novel are definitely indicated in the claims appended hereto. The construction and mode of operation of an inverse timclimit relay,embodyingthejn vention will be understood from the. m1: lowing description taken in connection with the accomp'anying drawings, in which;

Figure 1 is diagrammatic View in perspective of our novel and improved inverse time limit relay operatively connected to an electrical installation, and .Figs. 2 and 3 are explanatory diagrams.

vide in an inverse time limit relay having ment and the other contact member.

The inverse time limit relay of our inf vention comprises two movable contact members adapted to controlthe electric circuit of the tripping coil of a circuit breaking de-' vice. The two Contact members have coincident paths of movement and one contact whose distance from the initial. position of 'member is adapted to occupy a position the other contact member is an inverse func--;

tion of an electrical characteristidtrgph as the current consumption in an electrical in-' stallation, Whflle the. other contact member at a definite speed upon the 0mm- .rence of a predetermined overload in the installation One of the particular features of novelty of our present invention consists in providing means whereby the minimum time in which the two'contacrt members can move into engagement and complete the circuit of the tripping coil isadjustably determined. To this end, We provide an adjustv ember 1S adapted to move toward'the first contact able stop Which. determines lthe minimum' fdistance between the initial position of the Contact member having a definite move- In addition we have prov1ded a novel and 1111 proved means for actuating the movable contact member at a predetermined definite or uniform speed, and also means foradjustingthe time characteristic of the motion of this contact member. The means which We have devised for carrying out the objects of our invention Will behest understood by ref-y e'iencc to the accompanying drawings.

I Referring to Fig. 1 of the drawings there is diagrammatically illustrated conductors 4: 01; an alternating current electrical installation having translating devices 5 and provided With a circuit breaking device 6.

A series transformer 7 of the instrument transformer type is operatively related to the installation, and has its secondary Wind.- ing electrically connected. to the stationary curnent coil 8 of an inclined-coil ammeter of Well known design. A plurality of traps 63 a1'e brought out from the coil 8 so that a vatiable number of turns may be employed as the active ammeter coil, whereby the .same current flowing in the coil 8 may be .utili zed to produce variable effects upon the moving element of the ammeter by adjustingthe number of turns actively in cluded in the coil. In series with the seconda y winding of the transformer? and rninal member 28.

shaft 12. A damping disk 13 of aluminum, i

copper or similar conducting; metal is secured to the shaft 12 and is arranged to rotate between the poles of permanent magnets 1%. T he disk 13 and magnets 14 mag netically damp the movement of the moving element of the a'nn'ieter in the well understood manner.

The damping disk 13 has secured thereto a vane 1:3 which is adapted to engage with an adjustable fixed stop '16. Thefixed stop 16 is mounted in a slot-1.7 of a scale member 18 and is adapted to be adj u'stably fixed at iffiy position in. the slot by means of a set screw (36. The moving element of the ammeter and the disk 13 are represented in Fig. 1 of the drawings in substantially theirinitial or zero positions with. the vane 15 resting against a fixed pin 60. \Vhenev'or energy is being consumed in the translating devices 5, the disk 13 will move in a counter-clock wise direction, as viewed from above, and

the vane 15 will move toward the fixed stop 16. Theposition of the fixed stop lothus determines the maximum movement of the disk 13. A control spring 19 of the usual electrical instrun'ient type operatively re-.

lated to the shaft 12 and operates to 'exert' the necessary countertorque upon the moving element of the anuneter.

A contact member 20 is secured by means of a post 21 to the disk. 13. A flexible con ducting strip electrica ly connects the contact 20 to a terminalmember 23. A second contact member 2-1 is arranged to move in a. path coincident with the path of movement of the contact me .iber 20, and is secured to a pivotally mounted 'disk 25 by means of a ost 26, The/disk 25 1s adapted to be rotate at a definite speed by a mechanism. which will be described in detail hercinafter. A flexible conducting --;stri'p electrically connects the contact 24 to-"a ten The instantaneous overload relay 9 'is adapted to close the circuit oi" electroniag'nets '30-upon the occurrence of a predetermined overload in the electrical installation. The electronmgnets 30 are 'n'ovided with pole pieces 31 between which is arranged an armature member secured to a pivoted shaft A control spring 34. has one end secured to a fixed pin 35 and the other end secured to the shaft or) A movable contact iii-ember 3c is carried by the shaft and is opcrativcly related to a fixed contact member 23?.

An L-shaped arn'i 38 depends from the lower part ot the shaft 33 and has secured thereto one end of a control spring 39. other end of the control spring 39 is secured to a pivoted shaft 40 which carries the disk 25. The disk 25 is of conducting material, such as aluminum, copper, or similar metal, and is arranged to rotate between the poles of permanent magnets ll. The magnets ll are secured to a non-magnetic shoe -12. An adjusting screw-i3 is operatively related. to a stationary yoke M and en ages ina scrc threaded hole in the shoe It will thus be seen that the effective damping radius of the magnets 41 can be adjusted by turning the screw 43. The yoke 44 i. provided with a suitable scale 45 so that the effect of a movement of the magnets {ll can be calibrated. It will further be noticed that the periphery of the disk 27- is of spiral configuration whereby the; damping produced by the magnets ll is not constant throughout a position of the disk.

The

revolution of the disk but v'aries'with the An electromagnet 50 is operatively related ato the disk 13 and is arranged in'a manner similar to thatof the permanent magnets 1% The electromagnet has a winding 51 connected by conductor 52 to the terminal memJ ber 23 and by conductor 53 to the tripping eoilbl of the circuit breaking device 6. A conductor 55 connects the terminal member 28 to the terminalmember of the movable contact member 36. The stationary contact member 37 is connected to one conductor 56 of a direct; current installationywhile the other c0ndu'ctor'T57 of this direct currentinstallation is connected by conductor 58 to the tripping coil 'Itwill thus be seen that the tripping coil 54, the electromagnet winding 5'1,"the contacts .20 and 24, and the contacts'SG and 37 are arranged in series Lil) with each othcrand acros'sthc direct current conductors 56 and 57. The windings of the electromagnets 30 are also adapted to be connected across the conductors 56 and 57 by means of the instantaneous overload relay 9 An adjustable resistance 5-) is included incircuit with the windings of the clectromagiiets 30; The remaii'iing features of construction ofour-novel and improved inverse time limit relay will be best understood by a brief description of the operation thereof. The ap- 'waratus is norm ally inactive with no current flowing in thewindings of the clectromagnets 8O andSO. A current proportional to that being consumed =in the translating de vices 5 flows through the secondary winding of the transformer 7, the coil of the instan taneous'overload relay 9 and the ami'i'zeter coi- 8. The disk 13 therefore takes up a pcsition with respect to its zero determining respond to a minimum predetermined over- 1 Upon load in the electrical installation. the occurrence of any load greater than this predetermined overload, the instantaneous overload relay 9 will close the circuit of the windings of the electromagnets 30. The energization otthe electromagnefts causes the armature 32 to rotate in a clockwise (ii-1 rection thereby Winding up the spring 34 and bringing the cont-acts 36 and 37 ihto engagement. The movement of the arma ture is transmitted. to the L-shaped arm and rotates in a clockwise direction. The rotation of the disk is, however, damped or and energizes or Winds up the spring 39. The disk 25 begins immediately to respond to the influence of the energize-d spring 39 retarded by the permanent magnets ll, so. that its speed of rotation in response to the action of the spring 39 is substantially uniform. By means of the spiral configuration given. the periphery of the dish 25. the characteristic curve of movement of the disk can he i'ill'llody As illustrated in the drawings the damping efiiect of the magnets 41 upon the disk 25 is light at the beginning of the rotation otthe disk but increases as the disk rotates whereby a suitable modification of the shape of the time-current curve of the instrument may be effected. I

The contact member 24: rotates Withthe disk at a definite speed. The contact member 20, being secured to the disk 13 moves from its Zero positionas determined by the stop'BO in a coimter-clockwisedirec tion toward the contact member 2%, a distance which is a nieasure of the rate of current consumption in the translating devices It the overload continuesthe contact will engage with the contact 20. The engagement of? the "contacts 20 and 24 comp'letes the circuit of the tripping coil 54 whereupongthe circuit-breaking device 6 operatesto open the circuit of tliemranslating devices 5. The engagement of thecontacts 20 and also energizes the electrorhagnet 50. This vel ectromagnet may be termed a hiclcmagnet, since its function is to give the [disk 13 a slight forward movement .to accen tuate the engagement of the contacts '20'and 24. When the Winding 51 is energized by means of thetriiapingcurrent, eddy currents are set up in the disk 13. These eddy girrentsproduce the effect of a shaded pole motor Which is increased by the flux of the permanent magnets l l, which, due to its temporary motor etlect, gives the disk a quick kick thus forcing the contacts ZOfand' iZ-l more firmly together. This contact accentuating device more fully described and claimed in the copending application 'of dailies R. Craighead, tiled Sept. 20, 1916, Ser. No. 121,335. is connected across the Winding 51 and has the elieetof shunting a. certain amount of current from the Winding; 51, thus decreasng the kick action of the electromagnet 50.

By suitably proporti-oning the resistance (35 any desired; kick action can be obtained.

In all inverse time limit relays heretofore known to us there h'asbeen a certain definite overload for which the time of ope 'ation of all the relays in the installa- 'tion is the same. This condition is illustrated in Fi 2 of the drawings. [This figure represents "the" time-current curves A, B, and C of three different inverse time limit relays. lt will be evident that for a definite overload, represented by D along the current coiirdinate, each of the relays Will have identically thesame character-- istic time of operation. This is decidedly objectionable since it results in the'simnltane'ous operation of all the relays in the installation upon the occurrence or this particular overload. Obviously, it is desirable that therelaysmore remote from the central station. should operate sooner than those nearer the central station. One of the particular features of our invention is the provision of means whereby this result can be accomplished in the relay to which our inventions relates. In accorclance' with our invention, the adjustable fixed stop 16 is provided which determines the maximum movement of the contact 20.

i In this manner theminimum time in which A noninductive shunt 5 ice I which all the relays "would normally trip out, each curve has a definitebut different straight line time characteristic, whereby the minimum time in Which the various relays will ."energize their respective cooperating tripping coils isditl'erent for each relay.

The contacts; 20 and'fll are necessarily light since both are mounted on the moving elements of meter typeconstruction. The. contact 20 is a small platinum sheet iwhile thefcontact 24 is a small platinum springwith a small .straightend which slides over the contact 20. These two contacts are suitably insulated from the disks by which they are carried. These contacts are intended only to make and not to break the tripping circuit. The tripping circuit .is designed to be opened or broken by the relatively heavy contacts 36 and 37. To

this end, the spring 34: is considerably heavier than the spring 39. As soon as the circuit breaking device J3 has opened the circuit of the translating devices 5, the electromagnets 30 will be decnergized. The armature 32,immediately responds to the .action of the relatively heavy spring 3% initial position.

and returns almost instantaneously to its The contacts 36 and 37 are thereby separate-d, thus opening the tripping circuit. In the return movement of the armature 32, the Lshaped arnr '38 engages the pin. 61 and returns the disk.

25 to its initial position. The spring 3i is so proportioned that it is adapted to rotate the disk 25 agains the action of the magnets 41st a very rapid speed, so an,

thedisk 25 is returned to its initial post,

tion-with the .pin 61 resting against the fixed stop 62 substantially instantaneously.

Bythis arrangement the apparatus reset, in its initial condition substantially instantaneously after the actuation of the circuit breaking device '6. ltwill be apparent from the foregoing description that th-e contacts 36 and 37 disengage an instant sooner than the contacts '20 and. 24 whereby any sparkresultlng from the opening of the tripping circuit occurs at the contacts 36 and 37, thereby protecting the gages with the current dependent contact delicate contacts 20 and 24.

.. If the installation is relieved of the overload before the movable contact 2i en- '20, the. instantaneous overload relay 9 will open the circuit of the electrtmiagnets 30. The relatively heavy spring 34 then operates to immediately return the armature 32,

.thedisk 25, and the con'tact el to their initial positions, and the apparatus is almost instantantly restored to its initial condition in readiness to respond to another obtained and certainty of the correctorder of operation of circuit l'n'ealcing switches under all conditions is insured. The meter type construction utilized permits of the highest accuracy in the adjustments and operation Since one of the contacts,- nam ely contact 20 for closlng the circuit. of the tripping coil.

v of the apparatus. The use of two movable contacts whlch approach each other tOil'll) operation of the circuit breaking switchesis obtained by the adjustable stop 16 which causes the time characteristic" of the appa ratus to become definite for currents above any desired value.

The relay of our-invention is an inverse time limit relay but the time may be made definite for current values above any desired value by means of the maximum current stop 16 on the axnmeter element. The

general tendency of ti1nccurrent curves produced by most inverse time limit relays is to be very steep at the beginning, thus being very selective in respect to current, especially for small current values, but for any considerable current values the time becomes so small that selectively both ith respect to time and current is lost. Various attempts to improve these characteristics, for example, by means of inductive shunts, have in general'succeeded only in lifting the high current end of the curves, which separates the curves for different time settings and thus becomes selective in respect. to time. but the curves being made more fiat lose almost entirely their selectivity in respect to current except for very small currents. The clniracteristics ot' the timccurrent curves produced by our inverse time limit relay combine to a marked degree these two features,selectivity with respect to time and selectivity with respect to current. The curves are not so steep at the beginning but have a gradualslope through a wide range of tau-rent; selectivity with respect to current is, therefore, distributed through a wide range of current values and at the same time the currentfor'tlie' different time settings keeps well apart, being selective,

with respect to time.

The characteristics of the tiniie-current curve of our improved relay maybe moditied in three ways. First, by means of the different tape: on the current coil ot the ammeter element. As previously mentioned, the ammeter coil 8 has taps ()3 brought outwit. different numbers of turns ofthe' coil. Connections are made to the desired tap by means of a switch arm 64-.

54 is attached to the moving'element of the ammeter 1t wlll be seen that the taps 63 furnish a means for modifying the characteristics of the time-current curve, since the position whichthe moving element of the ammeter assumes upon a predetermined coil 8 can beadjusted by varying the nuin-J ber of active turns. Secondly, the'time characteristic of'the. time-current curve may be made definite for current values above any fixed point by means of the maximum current stop 16, thus preventing the time from becoming so small as to make the selectivity with respect to time doubtful. The relay is, of course, not selective with respect to current for current values above the setting of the maximum current stop. And thirdly, the time-current curve may be modified by adjusting the characteristic motion of the disk 25 and hence of the contact 24. To this end the dampin magnets 4C1 may be adjusted by means of he screw 48 to in crease or decrease their damping effect upon the disk 25, and the disk may further be given any peripheral configuration to produce the desired time motion of the contact 24. t 7

It will of course be understood that the movable contact 20 may be moved in response to any electrical characteristic of an electrical installation, for. example, in response to the voltage or wattage of an inby way of example for the purpose of ex- We have merely illustrated an. a'mmeter in the accompanyinig drawings movement of said second mentioned Contact as desired. 1 l

An inverse time limit relay comprising an electric circuit, a rotatable clement having an initial position, a spring adapted when energized to rotate said element, means for damping the rotation of said elcment, a contact included in said circuit and operatively related to said element, a second contact included in said circuit and posi tioned in the path of movement of said first mentioned contact, nieans whereby said second contact will occupy a position whose distance from the initial position of said first mentioned contact is aninverse function of the current consumption in an elec trical installation means for energizingsaid spring, and means whereby said element is returned to its initial position substantially instantaneously upon the engagement of said contacts.

3. An inverse time limit relay comprising an electric circuit, a rotatable element, a' spring adapted when energized to rotate said element, magnetic damping means for retarding the rotation of said element,

meansfor energizing said. spring, a contact included in said circuit and operatlvely related to said element, a second contact inplaining our invention. Thus, the movable contact 20 may be operatively related to the movable element of the wattmeter or voltmeter in exactly the same way that We have shown and'd'cscribed it operatively related to an ammeter.

Numerous modifications in the details of construction and design of our novel and improvedinverse time limit relay without departing from the spirit of our lnvent on will be apparent to those skilled in the art. Vi e do not, accordingly, desire to be limited to the specific construction herein illustrated and described by way of example for the purpose of explaining our invention, but we wish to cover by the appended claims all modifications and applications of-our invention within its spirit and scope. 1 What We claim as new and deslre to secure by Letters Patent of the United States, is v inverse time limit relaycompris ing an electric circuit, a movable contact having an initial 'position and included in said circuit, means for movin said contact at a definite speed, a second movable contact in cluded in said circuit and positioned in the path of movement of said first mentioned contact, means whereby said second movable contact willtoc'cupy aiposition whose distance from the initial position of said first mentioned contact is an inverse functioncof the cilrrent consumption in an electrical installation, and a stop member adj ustably positioned to limit the path of veluded in said circuit and positioned in the path-of movement of said first mentioned. contact, and means whereby said second contact will occupy a position whose distance from the initial position of said first mentioned contact is an inverse function of the current consumption in an electrical installation.

t. An inverse time limit relay comprising anelectric circuit, two cooperating contacts included in said circuit and adapted to move 1W5 toward "each other to complete the circuit, means whereby one of said contacts is adapted to occupy a position dependent upon the current consumption in anelectrical installation, means whereby the efiect of a predetermined current consumption upon the position of the current dependent contact may i be adjusted, means wherebythecsewond contact may bemoved toward the current dependent contact at a definite speed, an adjustable fixed stop adapted to limit the movement of the current dependent jconta'ct toward the second contact, and means whereby the rateof movement of the second ,contact may'be altered. I ma 5. An inverse time limit relay comprising an electric circuit, a rotatable element having an initial position, a spring adapted when energized to rotate said element, an electromagnet having a movable armature operatively connected to said spring, means for damping the rotation of said element, a contact included in said circuit and carried by said element, asecond movable contact tit having a path'ot movement coincident with that of said first mentioned contact, means whereby said second contact is adapted to occupy a position whose distance from the initial position of said first mentioned con- 1 tact is an inverse function of the current consumption in an electrical installatioi'i, and an adjustable stop adapted to limit the movement of said second conta t toward said first mentioned contact.

(3. An inverse time limit relay comprisin an electric circuit, a rotatable element, a

spring adapted when energized to rotate said element, means for damping'the rota tion of said element, a pair of cooperatiiig contacts included in said circuit, means for energizing; said spring whereupon the spring moves said contacts into circuit closing engagement to close said circuit, a third contact included in said circuit and operatively related to said element, a fourth contact included in said circuit and cooperating.

with said last mentioned contact, and means whereby said circuit is opened by the disengagement of said third and fourth contacts.

7. An inverse time limii relay comprising movement of the armature energizes the spring and operates to move said contacts into circuit-closing engagement, a second spring of greater strength than said first mentioned spring operatively related to said armature and adapted to return said armature and said element to their respective indial positions substantially instantaneously :upon the de'nergizing of said electromagnet, a third contact included in saidcircuit and operati'vely related to said element and havin an initial position, a fourth contact included in said circuit and cooperating with said last-mentioned COIli12LCl3,.IX1B?H1S whereby said fourth contact will occupy a position Whose distancefrom the initial positipn of said third contact is anfinverse r function of the current consumption in an electrical installation, and an adjustable stop adapted to determine the minimum distance between said fourth contact and the initial position of said third contact.

* 8. The combination with an electrical installation of an inverse time limitrelay comprising twomovable members arranged to I move toward each other, means for modifying the circuit conditions of said installation upon the engagement of said members, means-operative upon the occurrence of any overload in 'said installation exceeding a certain value for causing said members to essence which is an inverse function -o"f-the magnivalue and for causing said members to move into engagement in a constant definite time interval independent of the magnitude of the overoad when the magnitude of the overload is greater than said predetermined value, and means for adjusting the magnitude of the overload above which the memhers will engan'c in a constant time interval independent oi? the magnitude of the overload.

9. The coml'sination with an.-electrical in-- stallation of an inverse time limit relay comprising two movable members arranged to move toward each other, means whereby one of said members will. occupy a position dependent upon the current,consumption in the installation, means for moving the other member toward and into engagement with .the current dependent member upon the occurrence of a predetern'iined electrical condition in said installation a mechanical stop adjust-ably positioned to limit as do sire'dthe distance which the current dependent memher can more toward the other member, and means for modifying the cir cuit conditions of said installation upon the engagement of said members.

10. The con'ibination with an electrical in stallation, of a relay con'iprising two cooperating contacts, means for causing one of said contacts to take up a position which. is a m'easure of the current in the installatio'n, means for moving the other oi? said contacts in. response to an overload in said installation in excess of a'predetermined amount at a definite speed into engagen'ient with said positioned contact, and independerit' adjustable means for varying the extent of incremental said positioned contact.

1].. An inverse time limit relay comprising an electric circuit, two cooperating c0n tacts adapted 'to he moved into engagement to complete said circuit, means focmoving one of said contacts over a path to assume a position which. is a measure of an overload in an electrical installation, means for moving the other of said contacts into en'- gagemen't with said positioned contact at a move into engagement in atime interval definite speed, and separate adjustahle means for preventing the movement of said positioned contact beyond any prcdeten mined point in its path of travel.

l2. An inverse time limit relay comprising an electric circuit-,.1 two cooperating contacts adapted to he moved into engagement to complete said circuit, means for moving one of said contacts over a path to assume a position which is a measure of an overload in. an electrical installation, means for moving the other of said contacts into engage meat with said positioned contact at a definite speed, and an -fijustably positioned member coiipereting with said positioned contact to limit its path of movement.

13. The combination with an electric cireuit of an invei'setime limit relay comprising two eeiiperating contacts movable into engagement, an arnmeter element for cans" ingone of said contacts to take up aposition. which is the measui'e 0f the current consumed in said circuit, means for moving the other 0f seicla eontacts at a definite speed into engagement with said positioned centact, and mechanical means associated with said ammeter element to ad ustably cleten mine its extent of movement whereby the 3 pesitionef said positioned Contact is varied at will. i

In witness whereof we havelhereun to set ounhancls this 14th day of September, 1914.,

LEWIS T. ROBENSGN. CLYDE V. HARDY.

Witnesses: v

' BENJA Mm B. HULL.

Bem. H. VVEISBROD. 

